When the crankshaft main bearings have damage, it is also important to check the condition of the crank pins and connecting rod bearings as you have already done. If the crank pins look good and without damage, they can continue to be used. However, if the crank pin bearing has more damage, it should be replaced. As for discoloration of the crank pin surface, this can be caused by heat or surface oxidation. If this is the case, the surface can be cleaned and polished to remove the discoloration. However, if the surface has any imperfections, deep scratches or cracks, the surface should be replaced or repolished with a professional tool to keep the molar neck smooth and accurate.